GB potential evapotranspiration dataset

A few weeks ago I wrote about a method to derive incoming solar radiation for different latitudes. This was to help a GIS Masters student who’s looking to derive an equation for propwet that can be used to show the effects of catchment management changes. As an intermediate step the student also needed to calculate potential evapotranspiration. He did this on a catchment basis for Scotland. PE data is commercially available in the UK from the Met Office as part of their MORECS data.

Feeling inspired from my radiation success I’ve extended my previous efforts to calculate PE on a 5 km grid for Great Britain. I followed the methodology outlined by Kay and Davies, which only required temperature data (section 2.1.2) – extract below. To make life easier I followed the suggestion that sensible results can be obtained on a monthly aggregation. For temperature I downloaded the 1969-1999 long term average data available from the Met Office as part of their UKCIP09 assessment. This comes in a raster format, one grid for each month.

I just wanted to thank you for posting such a detailed run through of the methodology you used with the R script. I’ve been looking for a way of representing PET spatially with limited input parameters and I’ve managed to successfully adapt the R scripting techniques for use in my own project with slightly different data.

I didn’t know about the existence of the Kay and Davies paper and methodology. My first approaches, using Camargo’s ancient latitude-PET tables were failures, obtaining inconsistent results.
I used this as reference to calculate solar radiation and PET in the southern cone, and everything went just great. Now, those values are input to nice water balance models.
Thank you very much!